As a culture container for culturing cells, known in the art is a culture bag made of gas-permeable plastic used for filling culture medium therein. For example, Japanese Utility Model Application Laid-open Publication No. Hei 2-93999 discloses a culture bag in which a main body in the form of a bag made of a flexible plastic sheet has, in its upper portion, a solvent injection tube provided with a filter for separating micro-organism and also a culture medium outlet and a sterilized culture medium is filled in the main body of the bag. Japanese Utility Model Application Laid-open Publication No. Hei 3-172169 discloses a preservation and tissue culture container in which air-permeable sealing container for tissue culture containing a culture medium for tissue culture is sealingly wrapped with an impermeable material and this impermeable material is removed during tissue culture. Japanese Patent Application Laid-open Publication No. Hei 4-71482 discloses a method for manufacturing a culture bag filled with culture medium according to which culture medium which has been filtered for sterilization is filled in a sterilizing manner into a culture bag made of a film having large gas permeability and sterilized with γ-ray, the filling inlet is sealed in a sterilizing manner and then the culture bag is wrapped in a sterilizing manner with a secondary wrapping material which has small gas permeability and has been sterilized with γ-ray.